Automated external defibrillator with increased CPR administration time

ABSTRACT

An automated external defibrillator (AED) is described which spends an increased proportion of a rescue in a CPR mode. This is accomplished by use of a single shock protocol which causes the AED to spend less time in shock analysis and delivery activities as compared with the typical multiple shock protocol. An AED of the present invention preferably is configured such that the rescue protocol can be modified or changed easily without the need to remove the battery or use specialized hardware or software. Preferably the shock waveform of the single shock is a biphasic waveform delivering at least 150 Joules of energy and more preferably at least 200 Joules of energy.

This application is a divisional application of U.S. patent applicationSer. No. 12/096,756 filed on Jun. 9, 2008, which is a U.S. NationalStage Entry of International Patent Application No. PCT/IB2006/054707filed on Dec. 8, 2006, which in turn claims priority from U.S.Provisional Patent Application No. 60/751,268 filed on Dec. 16, 2005.

The invention relates generally to electrotherapy circuits, and moreparticularly, to automatic external defibrillators which provide forincreased proportions of time for the administration of CPR relative totime spent in the administration of defibrillation.

Automatic external defibrillators (“AEDs”) deliver a high-voltageimpulse to the heart in order to restore normal rhythm and contractilefunction in patients who are experiencing arrhythmia, such asventricular fibrillation (“VF”) or ventricular tachycardia (“VT”) thatis not accompanied by a palpable pulse. There are several classes ofdefibrillators, including manual defibrillators, implantabledefibrillators, and automatic external defibrillators. AEDs differ frommanual defibrillators in that AEDs they are pre-programmed toautomatically analyze the electrocardiogram (“ECG”) rhythm to determineif defibrillation is necessary and to provide administration measuressuch as shock sequences and CPR periods. There is no need, and in mostcases no ability, for a rescuer to be concerned with setup of the rescueprotocol. This differs from manual defibrillator which are used byexpert medical professionals skilled at setting up all of thedefibrillation parameters needed for a particular rescue.

FIG. 1 is an illustration of an AED 10 being applied by a user 12 toresuscitate a patient 14 suffering from cardiac arrest. In suddencardiac arrest, the patient is stricken with a life threateninginterruption to the normal heart rhythm, typically in the form of VF orVT that is not accompanied by a palpable pulse (i.e., shockable VT). InVF, the normal rhythmic ventricular contractions are replaced by rapid,irregular twitching that results in ineffective and severely reducedpumping by the heart. If normal rhythm is not restored within a timeframe commonly understood to be approximately 8 to 10 minutes, thepatient will die. Conversely, the quicker defibrillation can be appliedafter the onset of VF, the better the chances that the patient 14 willsurvive the cardiac event.

In the use of the AED a pair of electrodes 16 are applied across thechest of the patient 14 by the user 12 in order to acquire an ECG signalfrom the patient's heart. The defibrillator 10 then analyzes the ECGsignal for signs of arrhythmia. If a treatable arrhythmia is detected,the defibrillator 10 signals the user 12 that a shock is advised. Afterdetecting VF or other shockable rhythm, the user 12 then presses a shockbutton on the defibrillator 10 to deliver defibrillation pulse toresuscitate the patient 14.

Recent studies have shown that different patients may be resuscitatedmore effectively with different treatment regimes depending upon variousfactors. One factor which affects the likelihood of success ofdefibrillation is the amount of time that has elapsed since the patientexperienced the arrhythmia. This research has indicated that, dependingon the duration of cardiac arrest, a patient will have a betterprobability of recovery with one protocol as compared to another. If theAED is set up for a less effective protocol for the resuscitation of aparticular patient, that patient's probability of recovery may bereduced. These studies have shown that some of these patients have abetter chance of being resuscitated if CPR is performed first, to startsome circulation which may bring the patient to a condition whereapplication of a shock will be successful. There is also evidence thatan AED rescue protocol which provides CPR earlier in the cardiac rescueimproves the prospects for long-term survivability. Rescue protocolswhich provide for an uninterruptible CPR period are described in U.S.patent application No. 60/737,187 filed Nov. 16, 2005 and entitled “AEDHAVING MANDATORY PAUSE FOR ADMINISTERING CPR.” Furthermore, there isevidence that a rescue protocol which maximizes the proportion of CPRtime to defibrillation-related activity can improve survivability.Accordingly it is desirable to provide an AED which calls for CPR earlyduring a rescue and increases the ratio of the time allotted for CPRadministration relative to the time related to shock administration.

In accordance with the principles of the present invention, an AED isdescribed which provides for an increase in the proportion of CPR timerelative to time spent in shock administration activities. The AED ispreset prior to a rescue for a rescue protocol which, when a shock isadvised, will deliver a single biphasic shock of at least 150 Joules andpreferably of 175 Joules or greater. Preferably the single shockprotocol is pre-programmed as the default protocol for the AED Followingadministration of the single biphasic shock the AED goes into a CPRpause period during which CPR may be administered by the rescuer.

In accordance with a further aspect of the present invention the AED maybe easily set to the single shock protocol if currently set for amultiple shock protocol. Setting the single shock protocol may be donewith the user interface of the AED without removal of the battery.

In accordance with yet another aspect of the present invention the CPRpause period is followed by analysis of the ECG waveform and, if a shockis advised, either a single shock or multiple shock sequence isdelivered.

In the drawings:

FIG. 1 is an illustration of a defibrillator being applied to a patientsuffering from cardiac arrest.

FIG. 2 is a block diagram of a defibrillator constructed in accordancewith the principles of the present invention.

FIG. 3 illustrates an AED with an audible user interface.

FIG. 4 illustrates an AED with a visual user interface.

FIG. 5 illustrates a three-shock defibrillation protocol of the priorart.

FIG. 6 illustrates a single shock defibrillation rescue protocol of thepresent invention.

FIG. 7 illustrates a second single shock defibrillation protocol of thepresent invention.

FIG. 8 illustrates a single and multiple shock defibrillation protocolof the present invention.

FIG. 9 illustrates a third single shock defibrillation protocol of thepresent invention.

FIG. 10 is a detailed block diagram of a resuscitation predictorsuitable for use with a resuscitation protocol of the present invention.

FIG. 2 illustrates an AED 110 constructed in accordance with theprinciples of the present invention. The AED 110 is designed for smallphysical size, light weight, and relatively simple user interfacecapable of being operated by personnel without high training levels orwho otherwise would use the defibrillator 110 only infrequently. Incontrast, a paramedic or clinical (manual) defibrillator of the typegenerally carried by an emergency medical service (EMS) responder tendsto be larger, heavier, and have a more complex user interface capable ofsupporting a larger number of manual monitoring and analysis functionsand protocol settings.

An ECG front end circuit 202 is connected to a pair of electrodes 116that are connected across the chest of the patient 14. The ECG front endcircuit 202 operates to amplify, buffer, filter and digitize anelectrical ECG signal generated by the patient's heart to produce astream of digitized ECG samples. The digitized ECG samples are providedto a controller 206 that performs an analysis to detect VF, shockable VTor other shockable rhythm and, in accordance with the present invention,that performs a treatment regime which provides a relatively highproportion of CPR to the patient. If a shockable rhythm is detected, thecontroller 206 sends a signal to HV (high voltage) delivery circuit 208to charge a high voltage capacitor of circuit 208 in preparation fordelivering a shock, and a shock button on a user interface 214 isactivated to begin flashing. The rescuer is then advised by an audibleinstruction to keep away from the patient (“hands off” instruction).When the rescuer presses the shock button on the user interface 214 adefibrillation shock is delivered from the HV delivery circuit 208 tothe patient 14 through the electrodes 116.

The controller 206 is coupled to further receive input from a microphone212 to produce a voice strip. The analog audio signal from themicrophone 212 is preferably digitized to produce a stream of digitizedaudio samples which may be stored as part of an event summary 130 in amemory 218. The user interface 214 may consist of a display, an audiospeaker, and control buttons such as an on-off button and a shock buttonfor providing user control as well as visual and audible prompts. A userinterface of the present invention may also include one or more controlbuttons for selecting a rescue protocol stored in memory 218 to becarried out during a rescue. A clock 216 provides real-time or elapsedtime clock data to the controller 206 for time-stamping informationcontained in the event summary 130. The memory 218, implemented eitheras on-board RAM, a removable memory card, or a combination of differentmemory technologies, operates to store the event summary 130 digitallyas it is compiled during the treatment of the patient 14. The eventsummary 130 may include the streams of digitized ECG, audio samples, andother event data as previously described.

The AED of FIG. 2 has several treatment rescue protocols or treatmentmodes stored in which may be selected during setup of the AED when it isinitially received by the EMS service. One type of protocol is the“shock first” protocol. When the AED is set up for this protocol, theAED will, when connected to a patient and activated, immediately analyzethe patient's ECG heart rhythm to make a heart rhythm classification. Ifthe analysis determines that an arrhythmia treatable with electricaldefibrillation is present, typically either ventricular fibrillation(VF) or pulseless ventricular tachycardia (VT), the rescuer is informedand enabled to deliver the shock. If it is determined that thearrhythmia is not treatable with a defibrillation shock, the AED will gointo a “pause” mode during which CPR may be performed.

The second type of protocol is the “CPR first” protocol. When the AED isset up for this protocol, the AED will begin operating by instructingthe rescuer to administer CPR to the patient. After CPR is administeredfor a prescribed period of time, the AED begins to analyze the ECG datato see if an arrhythmia treatable with electrical defibrillation ispresent.

In accordance with the principles of the present invention the AED 110has the ability to execute either a multiple shock or single shockprotocol, the latter providing one or more periods for CPR which are agreater proportion of the time of the rescue in relation to the timespent by the AED in defibrillation shock-related activities, asdescribed in detail below. Preferably the single shock protocol is thedefault protocol, that is, the AED is preset for a single shock protocolat the time it is received by the EMS service. The AED can be set to thedefault setting at the factory or by a service person before it is putinto use by the EMS service. Thus, when the AED is received by the EMSservice it is ready for service immediately with the single shockprotocol after installation of the battery and the automatic executionof a self-test, with no further setup required. If the EMS serviceprefers a multiple shock protocol the protocol setting can be changed bya service person or by an AED administrator or other authorizedindividual of the EMS service to the desired protocol, as describedbelow. Preferably the protocol setting can be changed using the controlsof the user interface 214, and without undue manipulation complexitysuch as use of special hardware or software. It is preferable that theprotocol setting be changeable without the need to power down the AED.

In accordance with a further aspect of the present invention the singleshock protocol of the AED of FIG. 2 delivers a single biphasic shockwaveform rather than a monophasic pulse. The energy level delivered bythe single biphasic shock is at least as high as the energy level of ashock of the AED's multiple shock sequence. An energy level in excess of150 Joules is desirable with an energy level in excess of 175 Joulesbeing preferable and an energy level in excess of 200 Joules being morepreferable. (Actual delivered energies may differ somewhat from theintended dose delivery as a function of patient impedance.) In general,the single biphasic shock will usually be at or greater than the energylevel of the highest energy shock level of a multiple shock sequence.

Referring now to FIG. 3, an over-the-counter (OTC) AED 310 is shown in atop perspective view. The OTC AED 310 is housed in a rugged polymericcase 312 which protects the electronic circuitry inside the case andalso protects the layperson user from shocks. Attached to the case 312by electrical leads are a pair of electrode pads. In the embodiment ofFIG. 3 the electrode pads are in a cartridge 314 located in a recess onthe top side of the OTC AED 310. The electrode pads are accessed for useby pulling up on a handle 316 which allows removal of a plastic coverover the electrode pads. The user interface is on the right side of theAED 310. A small ready light 318 informs the user of the readiness ofthe OTC AED. In this embodiment the ready light blinks after the OTC AEDhas been properly set up and is ready for use. The ready light is onconstantly when the OTC AED is in use, and the ready light is off orflashes in an alerting color when the OTC AED needs attention.

Below the ready light is an on/off button 320. The on/off button ispressed to turn on the OTC AED for use. To turn off the OTC AED a userholds the on/off button down for one second or more. An informationbutton 322 flashes when information is available for the user. The userdepresses the information button to access the available information. Acaution light 324 blinks when the OTC AED is acquiring heartbeatinformation from the patient and lights continuously when a shock isadvised, alerting the rescuer and others that no one should be touchingthe patient during these times. Interaction with the patient while theheart signal is being acquired can introduce unwanted artifacts into thedetected ECG signal. A shock button 326 is depressed to deliver a shockafter the OTC AED informs the rescuer that a shock is advised. Aninfrared port 328 on the side of the OTC AED is used to transfer databetween the OTC AED and a computer. This data port finds used after apatient has been rescued and a physician desires to have the OTC AEDevent data downloaded to his or her computer for detailed analysis. Aspeaker 313 provides voice instructions to a rescuer to guide therescuer through the use of the OTC AED to treat a patient. A beeper 330is provided which “chirps” when the OTC AED needs attention such aselectrode pad replacement or a new battery.

When configured in accordance with the prior art the OTC AED 310 wasconfigured by the factory and shipped to customers with a three-shockdefault protocol. No instructions were given for a user to change theprotocol; if the owner or a potential rescuer desired a single shock orother protocol, the protocol could only be changed by an authorizedindividual using special setup software. However, when the OTC AED isdesigned in accordance with the present invention it is configured atthe factory for delivery to the customer with a single shock protocol asthe default protocol setting. In accordance with a further aspect of thepresent invention, the protocol can be changed from the user interfaceof the AED without removal of the battery or other specialized hardwareor software. An authorized individual depresses the information button322 three times or in another specialized sequence. This action causesthe speaker 313 to announce that the AED is in the setup mode and thelistener is given one or more options including protocol selection. Byfollowing the audible instructions the authorized individual is able tochange the default single shock protocol to another protocol setting orto modify the single shock protocol as illustrated below.

It will be appreciated that when the AED 310 is intended for laypersonuse without the assistance of trained EMS personnel, it will still bedesirable for adjustment of the protocol setting to be done only byauthorized personnel and not by layperson users of the AED.

FIG. 4 illustrates a defibrillator according to another example of thepresent invention. This AED 410 has a pair of electrodes 416 with aconnector 426 which is designed for insertion into a socket 428 on theAED 410. Located on a top surface of the AED 410 is the user interface,including an on-off switch 418 that activates the AED 410 and begins theprocess of audibly prompting the user to attach the electrodes 416 tothe patient 14. A status indicator 420 provides a continual visualindication of the defibrillator status and the available battery charge.A display 422 provides for display of text such as user prompts andgraphics such as ECG waveforms. A shock button 424 provides for deliveryof the shock to the patient 14 if ECG analysis indicates that ashockable rhythm is present. Administration of defibrillation shocks isdone by prompting the user 12 to manually press the shock button 424.

When configured in accordance with the prior art the AED 410 is providedto a customer with a three-shock protocol as the default protocol.Authorized individuals may change or adjust the treatment protocol toothers such as a single shock protocol by several different procedures.One procedure is to remove the battery of the AED and insert a speciallyconfigured setup card into the unit. When the battery is reinstalled theAED 410 will power up and show a setup menu on the display 422. Thedesired protocol changes can be made from the setup menu or by readingsetup data from the setup card. During setup the AED cannot be used fordefibrillation. At the completion of setup the AED is turned of and thebattery is removed again. The setup card is then removed from the AEDand the battery is reinstalled. The AED may now be powered up to the newsetup configuration.

Another procedure is to remove the battery and install a specializedadministration battery pack. While the administration battery pack isbeing installed the user holds down two option buttons 430 and 432 onthe user interface. When the AED 410 is powered up with theadministration battery pack installed, setup software is run to displaythe setup menu on the display 422. At the conclusion of the setupprocess the AED is powered down, the administration battery pack isremoved, the operational battery is reinstalled, and the AED may then beused in its new protocol configuration.

Yet another procedure is to receive new setup data by means of the AED'sinfrared port 328 (not shown in FIG. 4). The setup data can be receivedfrom a transmission by another AED 410 for by transmission from acomputer running specialized setup software.

In accordance with the principles of the present invention the AED 410is configured at the factory for delivery with a single shock protocolas the default protocol. The customer may then use the AED 410immediately after battery installation and self-test as a single shockAED. Any of the previously discussed procedures may be employed tochange the protocol to a multiple shock protocol or adjust the singleshock protocol as described below. Alternatively, the single shockprotocol may be modified for variation of the CPR period as discussedbelow and/or the protocol may be changed to a multiple shock protocolfrom the user interface without removal of the battery or communicationwith another AED or computer. A special depression of the user interfacebuttons such as holding down both option buttons 430 and 432 whiledepressing the shock button 424 or other specialized button sequenceenables authorized personnel to bring the setup menu to the display 422for modification and/or change of the shock treatment protocol.

Turning now to FIGS. 5 and 6, an illustration of the increasedproportion of time spent in CPR in a rescue protocol of the presentinvention is seen by a comparison of the two flowcharts. FIG. 5illustrates a flowchart of a typical three shock treatment protocol 500.At step 502 the AED begins by analyzing the patient's ECG waveform. If ashock is advised (the only outcome in these illustrations), the AEDcharges its high voltage circuitry and delivers a first shock at step504. After signal artifacts resulting from shock delivery havesufficiently dissipated the ECG is analyzed again at step 506 toascertain whether a normal heart rhythm has returned or another shock isrequired. If it is determined that another shock is advised, the AEDcharges the high voltage circuitry again and delivers a second shock at508. After delivery of the second shock the ECG waveform is analyzedagain at 510 to see if a normal heart rhythm has returned or a furthershock is required. If a shock is advised the AED charges and delivers athird shock at 512. Following the third shock in this example the AEDbegins a CPR pause period 514, during which time the rescuer may receiveaudible instructions in the administration of CPR. At the conclusion ofthe CPR pause period the ECG is analyzed to determine whether anothershock sequence is advised. It can be seen that the three shock sequenceof operation spends a considerable amount of time analyzing andpreparing for electrotherapy as compared to the time dedicated to CPR.

In comparison FIG. 6 illustrates a typical single shock sequence 600 ofthe present invention. As in the sequence of FIG. 5, this protocolbegins at 602 with the AED analyzing the ECG waveform to see whether ashock is advised. When a shock is advised the AED charges the highvoltage circuitry at 604 and delivers a single biphasic shock. Asmentioned previously, the single shock will deliver energy at the levelof the greatest level delivered by a shock of the three shock sequence,preferably at a level of 175 Joules or greater and more preferably at alevel of 200 Joules or greater. After delivery of the single shock theAED in this example goes into a CPR pause period at 606, during whichCPR is administered. At the end of the CPR period the AED analyzes theECG waveform at 608 to determine whether a normal heart rhythm hasreturned or another shock is required. ECG analysis may start during theCPR pause period if artifacts of chest compression are sufficientlyfiltered from the processed data. It is seen that a significantlygreater proportion of time is spent in CPR delivery during the singleshock sequence 600 as compared to the three shock sequence 500 of FIG.5.

FIG. 7 illustrates a second single shock protocol 700 of the presentinvention. The protocol 700 begins with ECG analysis at 702, charge anddelivery of a single shock at 704 when a shock is advised, and a CPRpause period at 706 followed by another analysis of the ECG waveform at708, all as previously discussed in FIG. 6. If a normal heart rhythm hasnot returned and another shock is advised, the AED charges and deliversanother single biphasic shock at 710. Following this second shockdelivery the AED enters another CPR pause period. It is seen in thisexample that every delivery of a defibrillation shock is followed by aperiod of CPR administration to provide a significant amount of CPRtreatment to the patient. Since the circulation promoted by CPR canincrease the prospect for a successful defibrillation, this protocol canoften result in a successful rescue, particularly for patients withsignificant downtime prior to rescue.

FIG. 8 illustrates a rescue protocol 800 of the present invention whichutilizes both a single shock and multiple shock sequences. This sequencebegins with the same four steps 802-808 as discussed previously. When ashock is advised after analysis of the ECG waveform at 808 the protocolbegins a three shock sequence by charging the high voltage circuitry anddelivering the first shock of the three shock sequence at 810. Afterdelivery of this first shock of three, the AED analyzes the ECG waveformto determine whether a normal heart rhythm has returned or a furthershock is advised. If a shock is advised the sequence continues withsteps 508-512 as discussed above before pausing for another CPR pauseperiod. The patient thus receives the benefits of both a single shockand a multiple shock sequence with this protocol.

FIG. 8 illustrates another protocol 900 of the present invention whichbegins immediately at 902 with administration of CPR. During or at theend of the CPR pause period the AED analyzes the ECG waveform at 904. Ifa shock is advised the AED charges and delivers a single biphasic shockat 906, followed by another CPR pause period at 908. Treatment continueswith steps 708 or 808 and their following steps for a single shock ormixed shock sequence, respectively. It is seen that the protocol 900provides the greatest percentage of time for CPR of the illustratedexemplary protocols.

The AED 110 of FIG. 2 has a further option, which is to recommend atreatment protocol, such as a shock first (e.g., FIG. 6) or CPR first(e.g., FIG. 9) protocol, as discussed more fully in concurrently filedU.S. patent application Ser. No. 11/917,212 entitled “DEFIBRILLATOR WITHAUTOMATIC SHOCK FIRST/CPR FIRST ALGORITHM.” This is done by the AEDwhich begins by analyzing the patient's ECG waveform and calculating andevaluating a return of spontaneous circulation (ROSC) score as describedbelow. From the evaluation of the ROSC score a treatment protocol isrecommended. The recommended protocol may be immediately carried out bythe AED, or the recommendation presented to the rescuer for his or herfinal decision on the treatment protocol to be carried out.

FIG. 10 illustrates a portion of the ECG front end circuit 202 andcontroller 206 of FIG. 2 which operate to recommend a treatment protocolwhich is likely to be effective for the patient. As previously mentionedthe electrodes 116 provide ECG signals from the patient which aresampled (digitized) by an A/D converter 20. The digitized ECG signalsare coupled to the ECG analysis processor in the controller whichanalyzes the ECG waveform to determine whether application of a shock isadvised. The ECG samples are coupled to a downsampler 22 whichsubsamples the stream of ECG samples to a lower data rate. For instance,a data stream of 200 samples/sec may be downsampled to 100 samples/sec.The downsampled ECG data is coupled to a ROSC calculator 24 whichdetermines a sequence of ROSC scores from the ECG data. The ROSC scoresare compared against a threshold by threshold comparator 26 to determinea mode of treatment which is most likely to lead to a successfulresuscitation. This mode determination is coupled to the mode selectionportion of the controller, which either selects the desired modeautomatically or presents the mode as a recommendation to the rescuerwho may then either decide to follow the recommended mode or analternate treatment regime.

The ROSC calculator 24 may be operated in several ways. For one example,the ROSC score can be calculated as the mean magnitude of the bandwidthlimited first derivative (or first difference, which is a discrete-timeanalog) of the ECG over a period of a few seconds. Since the bandwidthlimited first derivative may already be calculated for arrhythmiadetection by the controller 206, the additional computation may involveonly the additional calculation of an average. This process can beimplemented as a real-time measure by means of a moving averagerequiring only one addition and one subtraction per sample. Forinstance, the difference of successive samples may be taken for a streamof samples received over a period of 4.5 seconds at a 100 sample/secrate. The signs of the differences are discarded to produce absolutevalues, which are summed over the 4.5 second interval. This produces aROSC score value which is equivalent to a frequency weighted averageamplitude of the ECG waveform. The score may be scaled or furtherprocessed in accordance with the architecture and demands of the instantsystem.

Since the spectrum of the first derivative is proportional to frequency,the ROSC score is largely unaffected by CPR artifact, most of which willbe very low frequency.

Another alternative way to calculate a mean value is to square thedifferences of the consecutive samples, then sum the products and takethe square root of the sum. This produces an RMS (root mean square) formof ROSC score.

As an alternative to the mean value computation, another approach is touse the median magnitude of the first derivative. This approach is morecomputationally intensive, but can advantageously be more robust tonoise. Care must be taken to avoid de-emphasizing the signal that givesthe measure its discriminating power. In another embodiment, a trimmedmean or min-max calculation can offer a favorable compromise. Byeliminating the largest outliers, greater immunity to impulse artifacts(e.g. physical disturbances of the electrode pads) can be provided. Byeliminating the largest outliers, the occasional high amplitude artifactwhich would occur relatively infrequently can be eliminated withoutsignificantly reducing the discriminating power associated with the dataof cardiac origin.

What is claimed is:
 1. An automatic external defibrillator (AED)comprising: a pair of electrode pads; an ECG processor coupled to theelectrode pads and operable to analyze ECG signals to determine whethera shock is advised; a high voltage circuit coupled to the electrode padsfor the delivery of a biphasic defibrillation shock when a shock isadvised; a treatment protocol store which stores one or more treatmentprotocols including a single shock protocol by which the AED iscontrolled to deliver a single biphasic defibrillation shock that isalways immediately followed by a CPR period during which nodefibrillation shock can be delivered; and a controller coupled to thetreatment protocol store which operates to execute the single shockprotocol, wherein the single shock protocol is the default protocol forthe AED.
 2. The AED of claim 1 wherein the single shock protocol furtherdetermines, at the end of the CPR period, whether a normal heart rhythmhas returned or another shock is advised.
 3. The AED of claim 2 whereinthe treatment protocol store stores a plurality of treatment protocolsincluding the single shock protocol and at least one other treatmentprotocol, and each of the at least one other treatment protocol isselectable for execution by the controller.
 4. The AED of claim 3wherein the at least one other treatment protocol includes a multipleshock treatment protocol.
 5. The AED of claim 3 wherein the at least oneother treatment protocol includes a three shock treatment protocol. 6.The AED of claim 3 further comprising a user control interface operableby a user to select a user-selected treatment protocol from the at leastone other treatment protocol, the controller selecting the user-selectedtreatment protocol for execution by the controller.
 7. The AED of claim6 wherein the user control interface includes a display located on theAED for presenting the at least one other treatment protocol for userselection.